Physical durability, light fastness, and water fastness are the necessary requirements in many hard-copy imaging applications. Examples of such applications include outdoor signage, prints for security purposes such as passports or ID (identification) cards, CD (compact disk) labels, and lithographic printing plate.
Among the various digital output technologies, ink jet has the advantages of being non-impact, and having low-noise, low energy use, and low cost operation in addition to having the capability of being able to print on plain paper. These are largely responsible for the wide acceptance of ink jet apparatus in the marketplace.
An ink jet apparatus produces images on a receiver by ejecting ink droplets onto the receiver in an imagewise fashion. A frequently occurring problem associated with ink jet printing is excessive laydown of inks on the ink receiver. Image defects are often formed when inks are placed on the receiver at an amount or rate higher than the receiver can accept. For example, the ink spots placed at neighboring pixels on a receiver can come in contact with each other and coalesce, forming an image artifact commonly referred as "ink coalescence". Coalescence of ink spots on the receiver causes inks to diffuse or flow among ink pixels and results in a non-uniform or mottled appearance of the printed image. This ink diffusion problem is most visible at the boundaries of printed areas comprising different colors, where the ink of one color diffuses into the adjacent area of a different color ink to form a finger-shaped pattern. This latter image defect is commonly referred to as "color bleeding". Another need in ink jet printing is to provide an image on a receiver that is durable against physical abrasion.